Means for automatically controlling electric motors.



H. W. LEONARD.

MEANS FOR AUTOMATICALLY CONTROLLING ELECTRIC MOTORS.

APPLICATION FILED NOV. 7, 1907. 960,971 Patented June 7,1910.

'. WITNESSES I INVENTOR- fif ATTOHNEYS.

UNITED sTAr-Es PATENT OFFICE,

HARRY WAR-D LEONABl), OF'BBONXVIIJLE, NEW YORK.

MEANS FOR AIITOMATICALLY CONTROLLING ELECTRIC MOTORS.

Specification of Letters Patenh PatentedJune 7, 1910.

Original application filed February 6, 1897, Serial No. 822,269. Divided and application filed hm ary 28, 1902, Serial No. 91,577. Divided and this application filed November 7, 1807. Serial No. 401,055.

To all whom it may concern:

Be it known that I, ILiRRY 'WARD LEON- nm), a citizen of the United States, residing at Bronxville, in the county of Westchester and State of New York, have invented certain new anduseful Improvements in Means for Automatically Controlling Electric, Mo-

, tors, of which the following is a full, clear,

' and exact specification.

The present application is a division of my pending application filed January 28, 1902, Serial No. 91577, and renewed July 10, 1905, Serial No. 269132, and which was divided from my original-application Serial No.--622269, filed February 6, 1897, which resulted in Patent No. 717,58l, granted Jannary 6, 1903.

My invention relates to the control of electric motors and especially to the automatic control of electric motors in such a way that the motor will automatically operate to do just the amount of work re uired' of it. As illustrative,.it may be sai that it is frequently important that a pump be operated so as to maintain a certain level.

of water as in the draining of mines. The

amount of Water flowing 1nto the mine is of course variable and beyond control. By my invention an electric motor operating a pump will automatically pump at just the speed required to maintain the level of the wa ter constant regardless of the rate of inflow or outflow.

In a water supply system it is important that the pumping machinery shall..maintain a constant pressure on the mains, and in theme of compressed air, it is desirable that the air shall be maintained at a constant pressure independent of the demand. By my invention this is automatically accomplished in a very simple manner.

In the operation of certain machinery, it is desirable that means be provide'd which will'automatically protect the same from being exposed to excessive'strains. This can be readily accomplished by the use of my invention. For example, a hoisting apparatus'can be automatically stopped by my invention at a safe limiting position when it. might otherwise be driven beyond its safe limit of travel.

My invention is also ap licable to the operation from a source 0 power having a tolerably constant amount of energy at a tolerably constant speed, of machinery the torque element of the power of which may vary very widely, such as hoists, pumps, 10- comotives, etc.

Vith my invention I may use a prime m0- tor not very steady as to speed and secure constant speed at final motor by driving a centrifugal governor by the final motor which governor will-be the automatic regulator.

In' carrying my invention into effect I sometimes employ any well known form of automatic device, such as a float, a centrifugal governor, a. diaphragm or plunger operated by air, gas or water etc., to adjust a rheostat connected in the field circuit of a dynamo electric machine, which supplies a part or all of the energy for the working motor to be controlled, that is to say, instead of regulating the Working motor directly, I regulate its source of energy. In other words, I automatically cause to be varied the not effective volts delivered to the working motor to such a voltage as will operate the motor at the speed required.

Certain forms of my invention are illus trated in the accompanying drawings, in which-- Figure 1 is a diagrammatic view illustrating my invention applied to a porn ing system; and Fig. 2 is a similar view 0 another modification of my arrangement applied to a pum ing system. 7 i

' Referring to F1g."1 of the drawings in which my invent-ion is applied to a pumping system 0 crating in con3unction with an isolated lighting plant, A indicates a steam engine or other'prime mover driving dynamo electric machines B and (1- Conductors .1 and 2 extend from the machine B, between which are connected incandescent 'electric lamps L. The armature ofthe dynamo C is connected across the circuit 1- 2 in series with the armature of a working motor D. The dynamo C has a separately excited, variable and reversible field connected across the circuit 12 through an automatic re-' versingrheostat,the details of which will be hereinafter referred to. The field circuit of the working motor I) is a ractically con; stant one connected across t e circuit 1-2. Thus it will'be seen that by connecting the armature of the workin motor across the circuit 12 in series witi a dynamo whose field is variable and reversible, the Working 'motor may be operated at any speed from .zero to a speed due to the sum of the electro -motive forces of machines B and C, the electromotive forces of said machines being practically equal. That is to say, if the machines B and C are both 100-volt machines and both are producing their maximum electromotive force, and if the electromotive force ofmachine C is counter to-that of ma chine B, the working motor will receive no energy and will remain at rest. -N ow if the field of C be weakened, thus reducing the electromotive' force produced by that machine, the working motor will receive energy due-to the diiference between the electroinotive forces of B and C.- The energy so de livered to the working motor maybe-increased by decreasing the. strength of thefield of machine C until that machine is'producing practically no electromotive force, and then by reversing the field of that ma" chine, it will generate an GlBCtIOIDOtlXG force in'the same direction as that of machine 13,

and the working motor will receive an electromotive force equal to the sum of the elec tromotive forces of machines Band C, and. this eleetromotive force can be further 111- creased by lncreasmgthe strength of the field of. machine C, thus increasing the elec.

tromotive force produced thereby, and increasing the speed of the working motor, until the working motor receives the full electromotive force of the machines B and C.

The working motor drives a pump E whose outlet leads to a reservoir F, the water; in which must be maintained at a certain insulated from each other, a contact-plate g and resistances h and 71, connected with the conductors 7 and 8 respectively, which extend from the field magnet coils of' machine C. The position of the float and the automatic rheostat shown is one when the water in the reservoir is at the maximum level, that is, the entire resistance h is out of the field circuit of machine C, which machine then has a strong field and is generating'its maximum electromotive force, and

assuming that this electromotive force is equal and opposite to that of machine 13, the working motor will receive 'no energy.

. When the water in the reservoir falls below the maximumlevel, the fioat'descends 'and moves the contact-plates e and f upward, in-

serting a resistance in thefield circuit of the machine C,-thus weakenmg the field of that machine and gradually reducmg lts electromotive force, and hence the armature of the and hence increasing the energy delivered to the working motor. If the water in. the reservoir falls low enough to cause the floatto carry the contacts 6 and beyond the horizontal line, so that the plate a will bridge the plates g and Z), and the plate will bridge the resistance h and plate (Z, the 'field circuit of the machine C,Will be re versed, but with a weak field, so that a small electronioti've force will be generated by machine C in the same direction as that fromthe machine B; thus the armature of the working motor will receive an amount of energy due to the sum of the electromotive forces of the machines B and C and which amount of energy can be increased by strengthening the field of machine C. Thus it will be seen that the speed of the motor D may be gradually and automatically increased according to the fall of the water in the reservoir, and when the water in the reservoir begins to rise, the reverse action will take place and continue until. the-'watcr reaches the maximum level, when the automaticfrheostat will be again in its limiting position and the working motor will receive no energy. It will also be seen that the position of the controlling means will,adjust itself to cruise the motor to operate at a speed corresponding with the demand upon it for example, if the water is drawn from the tank-at a certain rate, then the controlling means will be automatically adjusted to cause the inotor to operate at a practi cally fixed speed corresponding to therequired rate of flow of the water. It will also be noted that machine G acts as a motor when its electromotive forccopposes and is less than that of the supply and act as a generator when its electromoti've force,

acts with that of the supply.

In Fig. :2, which shows another modification of my invention, the dynamo C-is driven by a motor C instead of by the prime mover as in Fig. 1. The motor C may be a shunt wound motor connected across the circuit l 2. The armatures of the machine C and working motor. D are in a local circuit 131t. By this arrangement the armature of the working motor receiveswnergy only from the machine C. The field coils of the machine C are connected by Wires 7, 8 across the main circuit 1-2 through a simplerheostat R controlled automatically by afloat in position and the motor -D is operating at anintermediate speed. i

It will be understood that the field strength of the motors C and D and generator B may be adjusted to any desired con- 'stant value by means of the rheostat in the field winding'indicated on the drawings.

By employing 2 dynamos as the source ofelectric energy, I- am able in certain instances to use relatively'smaller size dynamos, and I secure other advantages accruing by dividing 'the source into separate parts, as will be readily understood.

It will be understood that my invention may be embodied in various forms of con-' struction, and that I am limited in the scope thereof only as indicated by the following claims.

Having thus described my invention, I

declare thatwhat I claim as new and desire voltage of one of said two armatures relatively to the other for controlling the energy supplied to said motor winding.

- 2. The combination of two mechanically and electrically connected electromotive force producing windings, an energy absorbing device electrically connected thereto,

and means for automatically controllingfindependently of the strength of the current through the device,'.the voltage of the energy supplied by said electromotive force producing windings to said energy absorbing device.

3. The combination. of two mechanically connected elec'tromotive force producing windings electrically connected in series with each other, an energy absorbing device-electrically connected in series with said firstnamed windings, and means comprisingan automatically adjusted rheostat for automatically varying the resultant electromolive force of said windings for controlling the energy absorbed by the device.

4. The combination of two dynamo electric machines, a common driving means therefor, a field winding of one of said machines being excited independently of its armature current, means for automatically varying the current in said winding for varying the electromotive force, and a trans lating device supplied with energy from the armatures of said machines.

5. The combination of two mechanically andv electrically connected electro force producing windings, a counter elec motive force producing winding supplie with energy therefrom and requiring in operation variable voltage impressed at its terminals, and means for automatically controlling the energy supplied tosaid counter elect-romotive force producing winding:

6. The combination of two dynamo electric machines, a common driving means therefor, an electric motor, at least one of the windings of said motor being comiect-ed said machines connected in series with each other, and mea'nsfor automatically varying the relative electromotive forces of said machines for controlling the speed of the motor.

7. The combination of two mechanically and electrically connected electromotive force producing windings, a translating device, requiring in operation variable current strength and variable voltage, connected therewith, and means for automatically controlling the electromotive force of atleast one of said electromotive force producing windings for automatically controlling the operation of said translating device.

8. The combination of two dynamo electric machines, atleast one of said machines having a field winding energized by a current different from its armature current, a common means for driving said machines, a third dynamo electric machine, at least one of the elemental windings of said third machine being connected in a circuit containing the armatures of said two machines connected in series with each other, and means for automatically varying the combined electromotive force of said two machines for controlling the third machine.

9. The combination of two dynamo electric generators having their armatures connected in series with each other, at least one of said generators having a separately excited field winding, a common driving means therefor, and means for automatically varying the joint electromotive force across said two armatures.

10. The combination of two dynamo electric machines, a prime mover for driving said machines, an electric motor, at least one of the windings of said motor being connected in a circuit containing the electromotive force producing elements of said machines in series with each other, and means for automatically varying the combined elecin a circuit containing the. armatures of tromotive force and the current of said two each other, means formaintaining the speed of two of said machines fixed relatively to each other, and means for automatically varying the combined electromotive, force the current strength of the armatures said two machines for varying the mecnanical work done by the thirdmachine.

12. The combination of an electric motor, a pump driven thereby, and means for automatically controlling the performance of the motor and pump independently of a change in ohmic resistance of the motor armature circuit comprising a rheostat and a movable element automatically movable in response to the action of the fluid pumped for automatically moving the movable ele ment of 'said rheostat.

13.. The combination. of two electromotive force producing windings mechanically con-. nected together, an electric device requiring in operation variable voltage supplied with energy therefrom, and automatic means for varying the electromotive force of at least one of said windings for varying the vol-. tage impressed upon said device.

lhThe combination of a prime mover, a direct current dynamo electric machine driven thereby, said machine having a separately excited field. winding, and remote control means'for automatically varying the current in said field winding for varying the electromotive force of said machine.

15. The combination of a prime mover, a .direct current dynamo velectric machine driven thereby, said machine, having a separately excited ,field winding, remote control 1 tromotive force o means 'for automatically varying the current in said field winging for varying 'the elecsaid machine, and an electric motor liaving at least one element thereof supplied with the variable electrom otive 'force of said' machine.

16. The combination of a prime mover, a dynamo. electric machine driven. thereby, said .machine having a separately excited field winding, a dynamo electricmachine for supplying current to said firstmachine, an

. electric motor having its armature connected in series with the armature of saidfirstmachine,.and means for automatically varying the current in said field winding forv automatically varying the electromotive force of "said'first machine andthereby automatically varying the speed of the motor. 17. The combination of a dynamo electric machine, a prime source of power for driving said machine, a source of el'ectromotive force supplying current to afield winding of saidmachine, an electric motor having at least one of its elemental windings connect'ed in series with the armature of said machine, and means for automatically varying the current in said, field winding and thereby varyin the speed of the motor.

'18. The combination of a prime mover, a dynamo electric machine driven thereby and having a separately excited field winding, a

second dynamo electric machine driven. by sa1d,prime'mo ver'and"wh1 ch supplies cur- .rent to said field winding, a motor having at leastone of its elemental windings'connected in series with the armature of said first-named machine, and means for automatically varying the speed, of the motor.

-19.- The combination of a prime mover, a dynamo electric machine driven thereby and havin a separately excited field winding, a seconc dynamo electric machine drivem by said prime mover and which'supplies current to said fieldwinding, a motor having at least one of its elemental windings connected in series with the armature of said firstnamed machine, andmeans for automatically controlling the electromotive force of said first-named machine.

20. The combination of ,a. source of electromotive force, an electric motor supplied with energy therefrom, a pump driven by said motor, a rheostat having a movable element for varying the electromotive force of said source, and means for causing said element to respond directly to the condition of the fluid pumped.

I 21. The combination of an electric monected electromotive force producing wind ings for jointly controlling the energy in at least one of the elemental windings of the motor, and means comprising a field Windin said motor winding for automatically controlling the joint effect of said two windings for controlling tllB'IIlOtOL- 22. The combination of two mechanically connected electromotive fo'rce producin windings, a translating device controlle v thereby, and means for automatically resaid windings relatively to that of the other.

The combination of'an electric motor, a, mechanism driven thereby, and means for supplying variable voltage energy to at least one of the motor windings, said means comprising two mechanically connected elep- 'tromotive' force producing windin s.

24. The combination of aneleiric motor, a pump driven thereby, two mechanically connected ele'ctromotive force producing windings. for jointly controlling the energy supplied to at least one ofthe motor windings, and means controlled by the condition of the fluid pumped for automatically controlling said motor, v

The method of controlling the work performed by an electric motorwhich consists in generating two electromotive'forces in series with each other and with the counof the motor, and automatically varying at least one of the said two electromotive forces work to be performed by the motor.

26. The method of controlling the workperformed by an electric-motor which conter-electromotive force producing element tor, two mechanically and electrically coning energized by a current other than. that versing the electromotive force of one of,

in response to changes in the demand of the iso resultant voltage to the armature sists in generating two electromotive forces in series with" the armature of the motor, and automatically varying the resultant of the said two electromotive forces in response to changes in the demand of the work to be performed'by themotor.

27. The method of varying thevoltage impressed upon a circuit containing a translating-device for controlling the flow of a fluid, which comprises generating dynamically two voltages in series with each other,

driving said generators at same s eed, sup-' plying said voltages. to the trans ating de vice, and automatically varying one of said voltages between a negative value and a positive value in response to changes condition of the" fluid.

in the '28. The combination comprising two dy- -na1 nos,common means for driving the same, i a motor having its winding'connectedto th' arinatures of said dynamos, means operated by said motorfor' impelling the flow of a fluid, and a device res onsive-to changes in the condition of the uid for varying the voltage impressed on said motor winding.

29. The combination oritwo. dynamo electric arma'tures, common means for driving said a'rmatures, an electric motor winding in series with said armatures, a variable speed mechanism embodying a fluid, said speed mechanism being operated by, said motor,

. and means automatically operatedby the I pressing-said energy upon a winding of said voltage impressed on fluid for varying the.

' thus regulating said said motor winding, motor.

- .4 30. The method of automatically starting a motor employed'for controlling the flow rality of voltages by driving a'plurality of dyn'amos by a common means, supply-intgthei the motor, andcausing thefluidto automatically change said resultant fromzero.

31. The method. of pumping a. fluid by means of an electric device, which'comprises.

generating. dynamically electric energy, im-

of a fluid, which comprises generating a-plu f.

voltage .controllin device in the third cir- H cuit, controlling'tie current in said armature circuit bycausing the liquid to. directly operate said device.

33. The method of controlling an electric motor, which comprises driving two dynamos by a common means, collecting the generated energy distributing said energy in three circuits, energizing the field winding of'said'motor by one of said circuits, encrgizing the armature-winding by a second of said circuits, and controlling the energy in said second circuit by the energy otthc third of said circuits.

3d. The method of regulating a motor, v

which comprises driving two sources by a common means, eollectingthe electric energy generated, distributing said energy in three circuits in arallel with each other, energizing the fied'winding of said motor by one of said circuits, energizing the armature winding by a second of said circuits,-conthe energy; n the third of said circuits, and controlling the energy in the third ofsaid circuits b -the work done. by the motor, thus automatically controlling the energy in the motor circuit bylthe work done by themotor and independently of the current in the field-winding'of said motor.

In testimon whereof I flix my in presence-o 'twowitnesses.

HARRY 'WARD LEONARD,

\Vitnesses: v

" B. E. SMYTH'E,

O. J'. CORNELL.

: trolling the energyin said second circuit by signature, 

